package io.renren.common.utils;

/***
 * @date: 2024/3/18 13:50
 * @author liangpei
 * @param:  * @param null
 * @return: 雪花算法生成订单ID
 */
public class SnowflakeIdUtil {

    // 起始的时间戳
    private final long twepoch = 1288834974657L;

    // 机器id所占的位数
    private final long workerIdBits = 5L;

    // 数据标识id所占的位数
    private final long datacenterIdBits = 5L;

    // 最大机器id
    private final long maxWorkerId = -1L ^ (-1L << workerIdBits);

    // 最大数据标识id
    private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);

    // 序列在id中占的位数
    private final long sequenceBits = 12L;

    // 机器ID向左移12位
    private final long workerIdShift = sequenceBits;

    // 数据标识id向左移17位(12+5)
    private final long datacenterIdShift = sequenceBits + workerIdBits;

    // 时间截向左移22位(5+5+12)
    private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;

    // 序列的掩码
    private final long sequenceMask = -1L ^ (-1L << sequenceBits);

    // 上一次生成ID的时间截
    private long lastTimestamp = -1L;

    // 序列
    private long sequence = 0L;

    // 工作机器ID(0~31)
    private final long workerId;

    // 数据中心ID(0~31)
    private final long datacenterId;

    public SnowflakeIdUtil(long workerId, long datacenterId) {
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
        }
        this.workerId = workerId;
        this.datacenterId = datacenterId;
    }

    public synchronized long nextId() {
        long timestamp = timeGen();

        //如果当前时间小于上一次ID生成的时间戳，说明系统时钟回退过这个时候应当抛出异常
        if (timestamp < lastTimestamp) {
            throw new RuntimeException(
                    String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds",
                            lastTimestamp - timestamp));
        }

        //如果是同一时间生成的，则进行毫秒内序列
        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            // 毫秒内序列溢出
            if (sequence == 0) {
                //阻塞到下一个毫秒,获得新的时间戳
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            //时间戳改变，毫秒内序列重置
            sequence = 0L;
        }

        //上次生成ID的时间截
        lastTimestamp = timestamp;

        //移位并通过或运算拼到一起组成64位的ID
        return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
    }

    public static String getStrSnowId(long workerId, long datacenterId) {
        return String.valueOf(getLongSnowId(workerId, datacenterId));
    }

    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    protected long timeGen() {
        return System.currentTimeMillis();
    }

    public static long getLongSnowId(long workerId, long datacenterId) {
        SnowflakeIdUtil idWorker = new SnowflakeIdUtil(workerId, datacenterId);
        return idWorker.nextId();
    }

    public static void main(String[] args) {
        SnowflakeIdUtil idWorker = new SnowflakeIdUtil(0, 0);
        long id = idWorker.nextId();
        System.out.println(id);

    }
}